Water box and expansion chamber devices for such heat exchangers are already known in which the water box and the expansion chamber are made in a single piece of moulded plastic, the expansion chamber having an open end through which a moulding core is extracted and subsequently closed by an added-on cover which may be fitted with a fitting for filling the expansion chamber and suitable for receiving a stopper having safety valves for releasing too high or too low a pressure.
It is also known to provide a passage for degassing the liquid in such a device, said passage connecting the water box to the expansion chamber in such a manner that bubbles of air or gas transported by the liquid circulating through the water box can be injected into the expansion chamber by means of a relatively lower pressure existing in the expansion chamber. This prevents bubbles of air or gas from accumulating in various parts of the engine block which may lead to "hot points" which could damage the engine.
In the known technique, the degassing passage is often formed by an added-on tube which passes through the wall(s) separating the water box from the expansion chamber. To set up communication between the two different levels, the tube leaves from the upper part of the water box and ends beneath the free surface of the liquid contained in the expansion chamber. Placing such a tube and fixing it in place is not easy, particularly in mass production, and as a result the price of the device is increased.
Further, the water box of such a device is itself generally fitted with a tube for connection to the liquid circuit, said tube being integrally moulded with the water box.
In order to be able to fit the radiator in the limited space available in the engine compartment of a motor vehicle, this tube is sometimes required to have a particular disposition and orientation, thus posing moulding problems and, in particular, problems concerned with extracting the moulding cores which serve to define its inside surface. Proposals have already been made for solving this problem by providing a lateral core-extraction orifice in the tube. Said orifice being subsequently closed by means of a piece or plate of plastic material which may be welded in place ultrasonically, for example.
However, placing and welding the extra part also constitute additional operations in manufacture thus increasing the overall cost of the device.